1. Field of the Invention
The present invention relates to a flat fluorescent lamp, and, more particularly, to a flat fluorescent lamp comprising a main plate, whereby the structure of the flat fluorescent lamp is simplified, and the manufacture of the flat fluorescent lamp is easy. Also, the present invention relates to a method of manufacturing the same.
2. Description of the Related Art
Liquid crystal display (LCD) panels, which have been widely used in flat panel display devices, cannot emit light by themselves. As a result, backlight devices for providing a light source are attached to the liquid crystal display panels.
Backlight devices are classified into a direct-type backlight device and an edge-type backlight device. Such classification of the backlight devices is based on the position where the lamps are disposed. In the edge-type backlight device, the lamps are disposed at the edge of a transparent light guide panel such that light can be reflected and diffused through one surface of the light guide panel. As a result, a flat light source obtained through multiple reflection of light illuminates cells of the liquid crystal display panel. In the direct-type backlight device, on the other hand, the lamps are disposed directly under the cells of the liquid crystal display panel. A diffusion panel is disposed in front of the lamps, and a reflective panel is disposed at the rear of the lamps, such that light emitted from the light source can be reflected and diffused.
In the edge-type backlight device, brightness of the backlight device is moderate while uniformity of brightness is high. As a result, it is difficult to apply the edge-type backlight device to large-sized liquid crystal display panels. For this reason, the large-sized liquid crystal display panels mainly employ the direct-type backlight devices.
A conventional direct-type backlight device 1 is shown in FIG. 1.
FIG. 1 is a perspective view showing the structure of the conventional direct-type backlight device 1.
The direct-type backlight device 1 comprises a lamp unit 10, a reflective panel 20, a diffusion panel 30, and a prism sheet 40. The lamp unit 10 comprises a plurality of lamps 12, which may be either cold cathode fluorescent lamps (CCFLs) or external electrode fluorescent lamps (EEFLs). Irrespective of the fluorescent lamp used, the lamp unit 10 is constructed such that the lamps, each of which is formed in the shape of an elongated cylinder having a small diameter, are arranged in parallel with one another. When the cold cathode fluorescent lamps are used, it is necessary that inverters (not shown) be assigned to the respective lamps. When the external electrode fluorescent lamps are used, on the other hand, the lamps are driven by a single inverter. However, higher voltage must be applied to the external electrode fluorescent lamps than the cold cathode fluorescent lamps.
The reflective panel 20 is attached to the rear surface of the lamp unit 10 for reflecting light irradiated from the lamp unit 10 to the front surface of the lamp unit 10. The diffusion panel 30 and the prism sheet 40 are attached to the front surface of the lamp unit 10. The diffusion panel 30 serves to uniformly diffuse light, and the prism sheet 40 serves to guide the light diffused by the diffusion panel 30 in a straight line using a refraction phenomenon of light such that the light can be delivered to the cells of the liquid crystal display panel. A light guide panel may be attached to the front surface of the lamp unit 10 according to circumstance.
As the sizes of liquid crystal display panels are increased, the lengths of lamps used in the backlight device are also increased. For example, lamps each having a diameter of 4 mm and a length of 1000 to 1200 mm are used for 40-inch liquid crystal display televisions (LCD TVs). However, it is very difficult to manufacture the lamps with these dimensions. Furthermore, it is difficult to handle the narrow and elongated lamps when the backlight device is manufactured. The narrow and elongated lamps are very weak, and therefore, the narrow and elongated lamps may be easily damaged during handling of the narrow and elongated lamps.
The above-mentioned problems become increasingly serious as wide-screen liquid crystal display televisions are developed. For example, lamps each having a length of more than 2000 mm are required for 60-inch liquid crystal display televisions. However, it is not possible to manufacture such elongated lamps in accordance with conventional lamp manufacturing methods.